(57) A multi-shelf communication system for a communication switch having shelves is provided. There is a master generating commands and receiving status signals, slaves associated with the master, a communication controller per slave, a downstream communication link providing a multiplexed signal of communications from each controller and providing a demultiplexed signal split from the multiplexed signal to each slave, an upstream communication link from each slave to its controller, and a timing arrangement controlling transmission times for the downstream communication link. Each slave can be located on one the shelves and receives commands, executes local commands responsive to the commands and generates status signals for the master. Each controller receives commands, transmits commands to its slave and receives status signals and provides information relating to the status signals to the master controller. Local commands replace other commands directed by the master to the slave. Each slave communicates independently with the master.